Effects of beta-funaltrexamine and naloxonazine on single-trial morphine-conditioned place preference and locomotor activity.

TitleEffects of beta-funaltrexamine and naloxonazine on single-trial morphine-conditioned place preference and locomotor activity.
Publication TypeJournal Article
Year of Publication2003
JournalPharmacology, biochemistry, and behavior
Volume74
Issue3
Pagination617-22
ISSN0091-3057
Abstract

The current study assessed the ability of the selective irreversible mu-opioid receptor antagonists beta-funaltrexamine (betaFNA) and naloxonazine (NALZ) to alter the locomotor and rewarding effects of a single intravenous injection of morphine using the conditioned place preference (CPP) model. In the first experiment, rats were conditioned with a single injection of morphine (10 mg/kg iv) paired with one compartment of a CPP apparatus and then were tested for CPP at either 1 or 7 days after conditioning. Rats showed hypoactivity following acute morphine on the conditioning trial and showed CPP when tested either 1 or 7 days later. In the next experiments, rats were pretreated with betaFNA (20 mg/kg sc, 20 h before conditioning), NALZ (15 or 30 mg/kg sc, 24 h before conditioning) or saline and then were conditioned with a single injection of morphine (10 mg/kg iv) or saline. Pretreatment with NALZ alone, but not betaFNA, significantly decreased locomotor activity; neither antagonist alone produced a significant shift in preference for either compartment of the CPP apparatus. Pretreatment with either betaFNA or NALZ blocked completely morphine-induced hypoactivity, but neither antagonist had a significant effect on morphine CPP. These results indicate that mu-opioid receptors are more critically involved in acute morphine-induced hypoactivity than in acute morphine reward.

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0091305702010493
Short TitlePharmacol Biochem Behav
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